Field of the Invention
Embodiments of the present invention relate generally to ventilators and, more specifically, to techniques for determining patient airway pressure.
Description of the Related Art
A conventional ventilator is a mechanical device configured to move air into and out of the lungs of a user. The ventilator is typically coupled to an interface that is worn by the user, such as a tracheostomy tube, endotracheal tube, nasal mask or face mask, or nasal cannula. When the user inhales, the ventilator detects inspiration and pumps air through a delivery tube to the interface in order to create a positive pressure within that interface. The positive pressure forces air into the lungs of the user to assist with inhaling. When the user exhales, the ventilator detects expiration and allows air out of the delivery tube to reduce the pressure within the interface to allow exhalation.
Accurately determining the positive pressure generated within the interface during ventilation is critical in order for the ventilator to provide the prescribed therapy to the patient, limit excessive airway pressures and to provide indicative alarms to the user/clinician if the ventilator is not delivering the set pressure. Excessive pressures could be detrimental to the health of the user. For this reason, conventional ventilators usually employ some form of sensor configured to determine interface pressure or proximal airway pressure.
For example, designs could include a pressure transducer within the interface. The pressure transducer is linked to the ventilator and configured to report the measured pressure to the ventilator. If the interface pressure exceeds a maximum value, then the ventilator alerts the user. One problem with this type of design is that pressure transducers are bulky and therefore increase the size and weight of interfaces, potentially making these interfaces uncomfortable for the user. Another problem is that pressure transducers are generally far too bulky to be used in smaller nasal interfaces, and so users are required to rely on mask-type interfaces that cover the mouth and nose.
In view of these limitations, most designs place the pressure sensor proximate to the ventilator and then couple the pressure sensor to the interface via a secondary lumen, known in the art as the “sense tube.” The sense tube propagates pressure changes to the pressure transducer, which can then detect the interface pressure. This design is problematic, though, because adding a secondary lumen complicates the tubing between the ventilator and the user. One technique for simplifying such tubing is to integrate the sense tube directly into the delivery tube. However, such a design is generally too costly to implement.
As the foregoing illustrates, what is needed in the art is a more effective technique for determining the pressure within a ventilator interface.